In Regular Expression usually a pattern should be within the delimiters "/../" or even "|..|" can also be used.

The "\" (backslash) meta-character is used to specify that the next character as either a special character, a literal, a back reference, or an octal escape.

All these "^.[$()|*+?{\" special characters has to be escaped or treat as ordinary character using the backslash "\" symbol.

    $string = "T^he $[(value)] o|f + \can be a"
    Using the preg_match command in PHP following are the results.
    '/\^(.*)/' Result: ^he $[(value)] o|f + can be a
    '/\$(.*)/' Result: $[(value)] o|f + can be a
    '/\+(.*)/' Result: + can be a
    '/\((.*)/' Result: (value o|f + can be a
    '/\\(.*)/' Result: \can be a

    <?php
    $string = 'T^he $[(value o|f + can be a' ;
    preg_match('/\^(.*)/', $string, $matches);
    echo $matches[0];
    print "<br>";
    preg_match('/^(.*)/',$string, $matches);
    echo $matches[0];
    ?>

    ^he $[(value o|f + can be a
    T^he $[(value o|f + can be a 

In the above regex example we have matched the "^", with and without the "backslash", when used without the "\" the string is printed from the beginning as it behave's as a string, but when used without a backslash its print's a string from the beginning, as it behaves like a meta-character.

    #! C:\programfiles\perl\bin\perl
    print "content-type: text/html\n\n";
    if ("This is a (templateVar)" =~ m/[\(\)]/) 
      print "match!\n";
    else 
      print "no match!\n";

     match!

In the second example brackets "(" is escaped or made known as the next character using the backslash meta-character, since the string has brackets it matches.